Conventionally, the MPEG2 method is known for an image compression method of a moving image (refer to the following Patent document 1 or the like). In this MPEG2 method, moving images are classified into frame types such as the following (1) to (3), and image compression processing is switched for each frame.
(1) I picture: I picture is extracted every predetermined number of frames from the moving images, and this I picture is subjected to intra-frame compression.
(2) P picture: P picture located between the I pictures is extracted. A motion prediction frame is generated from the preceding I picture, and an inter-frame difference (inter-frame prediction difference) between the motion prediction frame and this P picture is obtained. Then the data of this inter-frame prediction difference is compressed.(3) B picture: B picture located between the I picture and the P picture is extracted. The motion prediction frame is generated from the preceding or succeeding I picture and P picture, and the inter-frame difference (inter-frame prediction difference) between the motion prediction frame and this B picture is obtained. Then, data of this inter-frame prediction difference is compressed.
Patent document 1: Japanese Unexamined Patent Application Publication No. 2005-12372 (paragraph [0002] and the like)